The invention relates to a bend segment for the upper part of the track of a chain conveyor comprising at least two spaced rails forming a track for the carrying surface of chain links and permanent magnets arranged below the track of the chain.
The invention also provides a bend segment for the return part of the track of a chain conveyor comprising two spaced rails for guiding the sides of the carrying surfaces of chain links.
EP-A-0 325 333 discloses such bend segments for the upper part and the return part of the track of a chain conveyor. Both the upper part and the return part comprise a U-shaped element, the magnets being arranged in the legs of the U-shaped element of the upper part at the upper face of these legs forming the rails for guiding the sides of the carrying surface of the chain links. In this known bend segment the legs of the U-shaped element for the upper part are open in the direction of the longitudinal axis of the bend segment and form a chamber for accommodating the magnets, the legs with the magnets therein are closed by means of a flexible strip or a further U-shaped element. The U-shaped element for the return part is provided with slots for guiding the sides of the carrying surfaces of the chain links.
EP-A-0 159 074 also discloses such a bend segment in which in the upper part the magnets are arranged in the legs of a U-shaped bend segment, and EP-A-0 286 173 also discloses such a bend segment in which the magnets are arranged in the connecting part between the legs of a U-shaped bend segment. In such bend segments the magnets serve to keep the carrying surfaces of the chain links containing a ferromagnetic material or completely made of ferromagnetic material flat on the track in the bend segments forming part of the track of a chain conveyor. Without the downward force exerted by the magnets the chain links, as a result of the pulling force exerted on the chain, tend to move upwards in the outer bend or even come off the bend owing to which the articles conveyed on the chain can fall off the chain, which is of course undesirable.
The known bend segments are largely made of polyethylene having an ultra-high molecular weight, so-called UHMWPE. This material is molded under high pressure into plates, from which plates the bend segments can be formed by milling. This method of manufacture has a number of drawbacks. In the first place, as a result of the milling process, much loss of material occurs, up to more than 50%, which makes the bend expensive. In the second place, the polyethylene, also if allowed to rest for a considerable period of time after molding, is not quite free from material stresses. Consequently, also after milling a bend segment is not quite free from stresses, which is undesirable.
Dutch patent application 1003738 discloses that, to save on the cost price of a bend segment, this bend segment is not manufactured by means of milling, but by means of injection molding. This solution is economical indeed, but has the drawback that, in particular for small series of one type of bend segment, the cost of the injection molding die is high. After all, each type of bend segment has its own die.
Furthermore, EP-A-0 207 577 discloses a bend segment for a chain conveyor consisting of spaced magnets each positioned around an axis, with ferromagnetic bushes placed against these magnets. Such magnet assemblies are provided against metal plate-shaped rails, on which rails chain links made of ferromagnetic metal run. Provided on the interior and exterior of the rails are different plastic filler and guide strips. This known bend segment can be easily manufactured in various dimensions, that is to say with different radii and lengths, and is relatively insensitive to fouling. A drawback is that the construction is very complex and can in no way be automated. Moreover, this known bend is only suitable for chains having a ferromagnetic carrying surface, because only at the upper side of the metal rails the magnetic field is sufficiently strong. The bend is not suitable for plastic chains of the type described in EP-A-0 286 173.
The object of the invention is to provide a fundamentally different solution for the manufacture of a bend segment for the track of a chain conveyor, for both metal and plastic chains, thus enabling a very easy and inexpensive manufacture of this bend segment with a very high flexibility, without the necessity of expensive dies for each type of bend and without an appreciable loss of material.
To this end, the invention provides a bend segment for the upper part of the track of a chain conveyor comprising at least two spaced rails forming a track for the carrying surface of chain links and permanent magnets arranged below the track of the chain, characterized in that a number of supporting elements for supporting the rails are provided, which supporting elements are spaced apart in the conveying direction of the conveyor, and that the permanent magnets are accommodated in chambers formed in an elongate strip which is also supported on the supporting elements.
Preferably, the rails, at least in the conveying plane of the conveyor, are flexible, because this enables rapid and simple assembly and requires no different rails for various radii. It is also possible, however, to give the rails a rigid design for special applications. Preferably, the strip with magnets is also flexible, but here, too, a rigid design is possible for special applications.
According to a first embodiment, the bend segment for the return part of the track of a chain conveyor according to the invention is characterized in that the guide rails, at least in the conveying plane of the conveyor, are flexible in the lateral direction and are supported by a number of supporting elements spaced apart in the conveying direction of the conveyor.
Preferably, a supporting element for the rails in the upper part is always attached to a supporting element for the U-shaped rails in the return part, with or without interposition of spacer elements. It is also possible to manufacture both supporting elements as a single injection molding product.
According to a preferred embodiment the rails of the upper part are connected with the supporting elements by means of a snap or sliding connection, for which purpose the supporting elements are provided with an element suitable for a snap or sliding connection, which element can couple with a part of the rails complementary thereto. Consequently, the rails can be easily replaced in the event of wear. According to a further preferred embodiment the guide rails for the return part are also complementary to at least a part of the slots formed at the underside of the supporting elements, so that the rails can be arranged in these slots by sliding or snapping.
According to a preferred embodiment the flexible strip containing the chambers for the magnets consists of a chain consisting of a number of individual links which are capable of being hingedly coupled together, while in at least a number of links at least one chamber is formed for receiving the magnets. The chambers are formed such that, if desired, the magnets and, if required, closure plates can be automatically placed in the chambers.
Preferably, the exterior of the links is provided with means capable of coupling by means of, for instance, a sliding or snap connection with complementary means at the supporting elements of the upper part, thus enabling attachment of the strip to the successive supporting elements.
By taking the measures according to the invention a bend segment for chain conveyors is provided which combines a very low cost price with a very high flexibility and an easy exchangeability of the parts subject to wear, in particular the rails.
One of the most important aspects of the flexibility is that bends of different radii and lengths can be easily made with the supporting elements and rails according to the invention, which bends are suitable both for metal (ferromagnetic) chains and for plastic chains having a ferromagnetic hinge pin. If the supporting elements have been made suitable therefor, both single and multiple bends can be designed. Consequently, it is no longer necessary to have different types of bends on stock. A further advantage is that the bend segment, due to its very open structure, can be cleaned very easily and effectively, and that coarser dirt, such as fragments of glass, crown corks etc., cannot lead to jamming of the conveyor, because this dirt can fall through the bottom construction to the ground. Also, due to the open structure, the sound production of the chain in the bend is substantially lower than with the known massive bend segments which actually form a sound box.
The range of applications of the strip consisting of links with magnet chambers formed therein according to the invention is not limited to the use with the supporting elements for a bend segment according to the invention, also with other bend segments for chain conveyors this strip may be advantageously used. For instance with the bend segment disclosed in DE-A-3 540 002 intended for use with so-called tab chains in which the tabs engage below the rails to keep the chain flat in the bend parts of the conveyor. Bend segments suitable for flexible conveying chains can be combined with the magnet strip according to the invention, the sides of the hinges being flat for tab chains or for chains in which the hinge loops are provided with beveled parts, the chains of the so-called bevel type.